1. Field of the Invention
The invention relates to a device and a method for determining the oscillatory behavior of a brake lining in the field of motor vehicles.
2. Description of the Related Art
The invention can be applied to a wide variety of brakes, such as those used for braking road vehicles, rail vehicles, aircraft or other means of transportation, as well as moving machine components. However, the invention and the problems on which it is based will be explained in more detail below using the example of a disk brake for a motor vehicle, in particular for an automobile.
Disk brakes use brake piston to press a brake lining against a brake disk that is undergoing movement. The brake disk usually is connected to a rotating part, such as a hub of a wheel on a motor vehicle. Sliding friction occurs in the contact face between the brake lining and the brake disk during the braking with a disk brake of this type. The kinetic energy of the rotating disk resulting from this friction is consumed and converted into heat. Plural brake pistons often are used to achieve a more uniform distribution of contact pressure over the contact face between the brake lining and brake disk.
Brake disks may be manufactured, for example, from gray cast iron, but also from ceramic composite materials. Ceramic composite materials may be advantageous in this context due to their lower weight, reduced wear and reduced corrosion tendency. Brake disks made of special ceramic fiber composites, referred to as carbon ceramic brake disks, also are used in vehicles.
The frictional material that contacts the brake disk during the braking process is attached, for example bonded, to a carrier plate or back plate that usually is fabricated from metallic materials.
A brake lining is pressed onto the rotating brake disk during a braking process. The sliding and at the same time frictional relative movement between the brake lining and the brake disk may cause oscillations to be excited in the brake lining. These oscillations may entail braking noises that are felt to be very unpleasant, particularly in motor vehicles, and efforts therefore are made to reduce these noises as far as possible.
However, since the actual oscillating system which includes the brake lining and from which the braking noises do not occur until when at least the essential components of a given disk brake of a specific type of motor vehicle are assembled, the detailed investigation of the braking noise which occurs in the driving mode entails a high degree of expenditure.
A selected brake disk and a selected brake lining can be installed in a motor vehicle and test runs can be carried out to investigate the noise behavior of the selected type of brake lining and the selected brake disk. Definitive information about the oscillatory behavior of the brake lining can be obtained on the basis of measurements during the test runs. However, such test runs are costly and time-consuming. The enormous amount of time expended on systematically determining and assessing the oscillatory behavior of different brake linings in contact with different types of brake disks is a severe impediment. Investigations on a brake lining installed in a vehicle are made even more difficult due to the usually poor accessibility of the installed brake lining.
DE 10 2005 059 015 B4 describes a noise testing arrangement for a disk brake where a brake lining acts on a rotating brake disk. Excitation of the oscillating system that may lead to braking noise is brought about in this arrangement by the sliding friction between the brake lining and the brake disk.
A systematic assessment of the noise generation of given brake linings used with a disk brake of a given design desirably should determine the oscillatory behavior of the brake lining accurately without the result being influenced by unknown details of the sliding friction process that are difficult to determine and under certain circumstances that vary over the service life of the disk brake.
The invention is therefore based on the object of making available a device and a method which permit, with little expenditure, systematic determination of the oscillatory behavior of a brake lining which is largely isolated from disruptive influences.